1. Field of the Invention
This invention relates to a display unit for projecting a small-sized display element on an enlarged scale, such as a liquid crystal projector.
2. Description of the Related Art
FIG. 14 shows an optical system of a liquid crystal projector in a related art. A light pencil emitted from a lamp 1 is reflected by a reflecting mirror 2 to form a roughly collimated light pencil 3. This collimated light pencil 3 is incident on a multilens array A4 and is divided into a plurality of light pencils. The provided light pencils are incident on a corresponding multilens array B5 and guide to a polarization conversion element 6 for making polarized light uniform. The light pencil with the polarized light made uniform is emitted through a condenser 7 as a condensed light pencil. The light pencil emitted through the condenser 7 changes in direction 90 degrees through a lens 8 and is incident on a dichroic mirror 20. The dichroic mirror 20 allows red light to pass through and reflects blue light and green light. The passing-through red light has an optical path bent through a reflecting mirror 22, undergoes a light beam angle correction through a collimator lens 9R, and illuminates a liquid crystal panel 10R. The green light and blue light reflected by the dichroic mirror 20 are incident on a dichroic mirror 21, which then reflects the green light and allows the blue light to pass through. The reflected green light undergoes a light beam angle correction through a collimator lens 9G and illuminates a liquid crystal panel 10G. The blue light passing through the dichroic mirror 21 has an optical path bent through a reflecting mirror 23, passes though a lens 18, and again has an optical path bent through a reflecting mirror 24. Then, the blue light passes through a collimator lens 9B and illuminates a liquid crystal panel 10B.
The liquid crystal panel 10R modulates the projected light by a red video signal and displays an image. Thus, the light is allowed to pass through or is shielded selectively on the liquid crystal panel. The passing-through light is incident on a dichroic prism 11, has an optical path bent by a reflection face 11R, and is incident on a projection lens 12. The liquid crystal panel 10G modulates the projected light by a green video signal and the light passing through the liquid crystal panel 10G is incident on the dichroic prism 11 and is incident on the projection lens 12 as it is. Likewise, the light incident on the liquid crystal panel 10B is incident on the dichroic prism 11, has an optical path bent by a reflection face 11B, and is incident on the projection lens 12. The red light, green light, and blue light incident on the projection lens 12 are combined and projected on an enlarged scale as a full-color image.
FIG. 15 shows a part of the optical path of the projection display unit in the related art.
FIG. 15 shows a state in which the optical path from the lamp 1 through the liquid crystal panel 10G to the projection lens 12 is extracted from the optical path in FIG. 14 and is aligned on a line without showing the mirrors for changing the light beam directions. However, the dichroic prism 11 is not shown.
The light pencil emitted from the lamp 1 is reflected by the reflecting mirror 2 to form the collimated light pencil 3. The collimated light pencil 3 is divided into a plurality of light pencils through the multilens array A4 for narrowing the light pencil toward the corresponding multilens array B5. The multilens array B5 has a role of maintaining the corresponding multilens array A4 and the display element 10 in conjugate relation. The light pencils passing through the multilens array B5 are incident on the polarization conversion element 6 and are divided into two linearly polarized light pencils orthogonal to each other. One of the light pencils rotates the vibration face of the polarized light 90 degrees by means of a phase difference plate 13 disposed on the emission face of the polarization conversion element 6. Therefore, all light incident on the condenser 7 becomes linearly polarized light with the vibration face made uniform. The condenser 7 has a role of superposing images of the multilens array A4 formed on the multilens array B5 on the display element 10. The collimator lens 9 before the display element 10 has a role of making even incidence angles of light beams in the display element 10 plane.
In FIG. 15, attention is focused on a light beam angle 14 toward the center of the display element 10. The magnitude of the light beam angle 14 is almost inversely proportional to the distance from the condenser 7 to the display element and is almost proportional to the light pencil diameter passing through the condenser 7. Since the light passing through the display element 10 is input to the projection lens 12 and is projected on an enlarged scale, the light incidence angle 14 on the display element 10 needs to be made equal to an input angle 19 to the projection lens 12.
The projection display unit in the related art is thus configured, wherein the projection lens 12 is limited by the magnitude of the input angle 19 and the outer dimensions of projection lens 12 are determined. The characteristics of the resolution, distortion of a projection screen, and uniformity of brightness in a projection screen, performance proper to the projection lens 12 make it difficult to design and manufacture as the input angle 19 grows; this is a problem.
Further, if the length from the condenser 7 to the display element 10 is lengthened, as shown in FIG. 16, to lessen the light beam angle 14 or the input angle 19, the placement space of the parts needs to be taken larger than that in FIG. 15 and thus the outside shape of the projection display unit becomes large; this is a problem.
Alternatively, if a method of lessening the light pencil diameter passing through the condenser 7 for lessening the light beam angle 14 or the input angle 19 is adopted as shown in FIG. 17, the following problems arise: A sufficient amount of light does not arrive at the display element 10, heat is generated due to light lost by lessening the light pencil diameter, stray light is produced due to scattering of light, etc.
It is therefore an object of the invention to provide a small-sized system comprising a lens for correcting a light pencil incident on a display element or the light beam angle of the light pencil. It is another object of the invention to provide a system good in light use efficiency by placing the numbers of lens cells and the lens cell sizes of two multilens arrays used with a projection display unit in appropriate relationship.
In order to achieve the above objects, according to a first aspect of the invention, there is provided a projection display unit comprising: a light source for projecting an image; a reflecting mirror for reflecting a light pencil emitted from the light source; a first multilens array for dividing a light pencil gathered by the reflecting mirror into a plurality of light pencils; a second multilens array for forming an image of light pencil emitted from the first multilens array; a polarization conversion element for converting light pencils in an irregular polarization state emitted from the second multi lens array into linearly polarized light; a condenser having positive power for superposing the light pencils provided through the second multilens array; a collimator lens having positive power for correcting the angle of a light beam; a display element for forming an image by electric modulation; a projection lens for enlarging and projecting the image formed on the display element; and a correction lens being disposed between the condenser and the collimator lens for correcting a light pencil incident on the display element.
According to a second aspect of the invention, there is provided a projection display unit comprising: a light source for projecting an image; a reflecting mirror for reflecting a light pencil emitted from the light source; a first multilens array for dividing a light pencil gathered by the reflecting mirror into a plurality of light pencils; a second multilens array for forming an image of light pencil emitted from the first multilens array; a polarization conversion element for converting light pencils in an irregular polarization state emitted from the second multilens array into linearly polarized light; a condenser having positive power for superposing the light pencils provided through the second multilens array; a collimator lens having positive power for correcting the angle of a light beam; a display element for forming an image by electric modulation; and a projection lens for enlarging and projecting the image formed on the display element, wherein the number of lens cells of the second multilens array is less than that of the first multilens array.
According to a third aspect of the invention, there is provided a projection display unit comprising: a light source for projecting an image; a reflecting mirror for reflecting a light pencil emitted from the light source; a first multilens array for dividing a light pencil gathered by the reflecting mirror into a plurality of light pencils; a second multilens array for forming an image of light pencil emitted from the first multilens array; a polarization conversion element for converting light pencils in an irregular polarization state emitted from the second multilens array into linearly polarized light; a condenser having positive power for superposing the light pencils provided through the second multilens array; a collimator lens having positive power for correcting the angle of a light beam; a display element for forming an image by electric modulation; and a projection lens for enlarging and projecting the image formed on the display element, wherein the second multilens array has lens cells sized larger than those of the first multilens array.